1. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman1 Heavy Ion Physics with CMS Dave Hofman UIC for the CMS Collaboration CMS Heavy-Ion Groups Athens, Auckland, Budapest, CERN, Chongbuk, Colorado, Cukurova, Iowa, Kansas, Korea, Los Alamos, Lyon, Maryland, Minnesota, MIT, Moscow, Mumbai, Rice, Seoul, Vanderbilt, UC Davis, UI Chicago, Zagreb HI Collaborators - 64 PhDs, 35 Students Overall CMS Collaboration 38 Countries, 181 Institutions, ~2500 Scientists

2. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman2 Brief (US-centric) History of Heavy Ions in CMS HI physics included in all CMS reports starting from first proposal. 2002 Entry of US groups* * Davis, LBNL, Rice already active in CMS HI – CMS Note 2000/060 2003-2006 Greece, Hungary, India, Korea, N.Zealand, Turkey 1994 CMS HI started by Russian & French groups 2006 - Proposal to DoE for US HI@CMS 2007 - CMS TDR for Heavy Ion Physics Recent Milestones Table of Contents Introduction Global observables and event characterization Low p T hadron spectra Elliptic Flow Hard probes triggering capabilities Quarkonia and heavy- quarks Jets and high-p T hadrons Ultraperipheral collisions 2006 – Successful ZDC Test Beam

3. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman3 Heavy Ions in CMS Pb+Pb event (dN/dy| y=0 = 3500) with      - World-class capabilities in hard probes. Complementary (& surprising) abilities for soft physics and global observables. Unique opportunities and capabilities in forward region. Sophisticated high-rate triggering to exploit and maximize physics output. +

4. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman4 The Compact Muon Solenoidal Detector CASTOR T2 Collarshielding Forward Detectors (5.2 < |  < 6.5) TOTEM ZDC (5.3 < |  < 6.7) (|  > 8.3, z =  140 m) Beams EM HAD Forward Calorimeter (3 <  < 5.2) Solenoid Return Yoke Si TrackerEcal Hcal Muons Silicon and  Tracker  ECAL  HCAL 

5. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman5 Particle Detection in CMS Tracking + Ecal + Hcal + Muons for |  |<2.4 Silicon Microstrips and Pixels Si TRACKER CALORIMETERS ECAL Scintillating PbWO 4 crystals HCAL Plastic scintillator/brass sandwich MUON BARREL Drift Tube Chambers (DT) Resistive Plate Chambers (RPC)

6. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman6 Tracking Performance at Low p T All Tracker Fitting Low p T Tracking Using Three Pixel Layers PID with dE/dx and Topology (V 0 ) Pixel Tracking Si Tracker Pixel Detector Occupancy of < 2% Including Pulse Height Information Tracking at low p T Multiplicity (entries)

7. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman7 Tracking Performance at High p T Momentum Resolution Track-Pointing ResolutionEfficiency/Fake-rate Inclusive p T Spectra vs Collision Centrality –Determine Nuclear Modification Factors R AA –Yield plus High Level Trigger will allow Measurement out to >200 GeV. Statistical Reach (using HLT) 0-10% central Efficiency o Fake Rate p T [GeV/c] Percentage (%) p T [GeV/c] Resolution (%) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 o 2.0 < |  < 2.5 0.0< |  | < 0.5 p T [GeV/c] 250 200 150 100 50 0  t (  m) o 2.0 < |  < 2.5 0.0 < |  | < 0.5

8. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman8 Jet Reconstruction CALORIMETRY Efficiency, Purity Jet Energy Resolution ~18%  9% JET FINDING ALGORITHM FOR HI + TRACKING + TRACKING Azimuthal correlations: dN/d(  )  (rad) Fragmentation functions: 1/N jets dN ch /dz p T with respect to jet axis: 1/N jets dN ch /dp T jet p T jet (GeV/c) Pb+Pb dN ch /d  |  =0 ~5000 + 100 GeV jets Recalculate background outside cone + recalculate jet energy Subtract “background” Find jets with iterative cone algorithm

9. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman9 Quarkonia  = 35 MeV/c 2  = 54 MeV/c 2  ’’  ’’ MUONS + TRACKING MUONS + TRACKING J/   family  ’/  Statistical Reach (using HLT) parton gas i parton gas ii minijet ii minijet i

10. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman10 High Mass Di-Muons Z 0     reconstructed with high efficiency by design Dimuon continuum dominated by b decays High statistics Balance Energies of  */Z 0 and Jet  , Z 0

11. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman11 Excellent Event Characterizations Event Selection and Centrality Determination “Spectators” ZDC ZDC Forward HCal CASTOR Forward HCal CASTOR Energy in Forward HCal E T [GeV] impact parameter [fm] Pb+Pb Zero Degree Calorimeter

12. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman12 Forward Physics Quarkonia photoproduction Uses ZDC to trigger on forward emitted neutrons Measurement  ->  +  -, e + e - in the central detector Probes nuclear PDF in unexplored (x,Q 2 ) range

13. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman13 CMS Trigger Level 1 Trigger (LV1) Uses custom hardware Muon chamber + calorimeter information Decision after ~ 3  sec High Level Trigger (HLT) ~ 1500 Linux servers (~12k CPU cores) Full event information available Runs “offline” algorithms Level-1p+pPb+Pb Collision Rate1 GHz3 kHz (8 kHz peak) Event Rate40 MHz3 kHz (8 kHz peak) Output Bandwidth100 GByte/sec Rejection99.7%none High Level Trigerp+pPb+Pb Input Event Rate100 kHz3 kHz (8 kHz peak) Output Bandwidth225 MByte/sec Output Rate150 Hz10-100 Hz Rejection99.85%97-99.7% Primary “hardware” task for CMS heavy ion running

14. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman14 Heavy Ion Trigger Strategy Select all minimum bias Pb+Pb events at Level 1 Send full event stream to the High Level Trigger Run “offline” algorithms on every Pb+Pb event –Select Hard Probes embedded in highly complex events –Examples: Jet finding algorithm, dimuon reconstruction –Best selection needs full event information and complex algorithms Maximize Physics Signals of Interest

15. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman15 HLT Physics Enhancement Jet trigger and R AA Results for one full luminosity LHC heavy ion run (10 6 sec) More than 10x Gain for Di-Muons (factors of 2-3 for low-luminosity running) Minimum Bias StreamJet Trigger Stream 0-10% central

16. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman16 Role of US Physicists Leadership RHIC experience Physics Analysis Triggering and Data Acquisition Zero Degree Calorimeter Offline Computing for Heavy Ions

17. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman17 Final Thoughts CMS is a Superb and Versatile Detector for Heavy Ion Physics at the LHC Excellent performance in high p T (E T ) region and for  pairs – by design Capability for global/soft physics Unique forward physics capabilities & coverage Sophisticated trigger will extend physics reach and allow us to focus on key physics issues The detector and data acquisition are uniquely suited to the multi- purpose nature of the LHC The US Nuclear groups are providing leadership to the well established CMS HI effort Extremely large physics return in a very short time-scale

18. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman18 Backups

19. Phases of QCD Matter Town Meeting, Rutgers, Jan 12-14 2007Dave Hofman19 HLT Physics Enhancement Example Statistical SignificanceRates to Tape Results for one full luminosity LHC heavy ion run (10 6 sec)